1. Field of the Invention
The invention relates to the field of communications. More specifically, the invention relates to error correction in communications.
2. Background of the Invention
In communication networks, forward error correction (FEC) is used to protect transmitted information from impairments that occur while being transported in a transmission system. In the case of algebraic block codes (e.g. the Reed Solomon code), redundancy symbols are added to the information symbols before transmission of a block of symbols. A network element that receives the transmission can correct transmission errors as long as the number of corrupted symbols does not exceed a certain threshold given by the special construction of the code.
An alternative to algebraic coding is iterative coding. Iterative coding algorithms have been developed for correction of streams of transmitted information where scalar information representing the reliability of a received symbol of the stream of transmitted information is available. These iterative coding algorithms are also referred to as soft-decision algorithms.
However, soft-decision coding techniques generally do not apply in optical networks where high transmission rates interfere with the ability to generate reliability information for received symbols. Moreover, soft-decision coding algorithms tend to have relatively poor performance for streams of transmitted information with low probability of bit errors after correction, which occurs in optical networks.